Air Volume? 590MM barrel?

aight hope you guys are having a good day, so im on the process of converting my KWA into a DMR and i was planning the inner barrel to be 590 mm, but i came across things that said you need the right air volume to make the bb roll out of the barrel, i have a ported cylinder, can someone explain to me or list me the things im supposed to get? Also, i can't find 590 6.01 prommies only 6.03s, does that affect accuracy in a good way or bad way? im just looking to get my kwa mod 2 into a dmr with the best accuracy i can achieve, money isn't a obstacle but im not buying another gun to turn it into a dmr and leave the cqr by itself, im willing to install any piece required, currently it has been reshimmed, a jg wiring, and a firefly buffer rubber hard type hop up nub, im also running a 11.1 lipo, FPS isn't something i really care about since it doesn't make a change into accuracy but if it is needed to be pumped up i will do it as long as it doesn't go past 400, i appreciate the help!

why 590mm? you'll need a full cylinder. but with a M120 spring, you'll probably be over 400fps with 0.20gm bbs.
With my SR12, I have a 509mm 6.01mm PDI inner barrel, with the stock M120 spring and that gets me to about 390fps.

I agree. Although in real steel, longer usually means more accurate, in airsoft this is not necessarily the case. I highly recommend you read Vanevery's post titled "Let's Talk Long Range." I believe it would be very beneficial to you. Under his direction, with not too much money, I have been able to build my SR10 into a very accurate rifle. More so than my friend's Ares M110, which obviously has a longer barrel. I was making shots at about 275 feet with an almost 12 mph crosswind. Again, I recommend you find Vanevery's post and ask him some questions. I believe it's in community general chat.

I agree. Although in real steel, longer usually means more accurate, in airsoft this is not necessarily the case. I highly recommend you read Vanevery's post titled "Let's Talk Long Range." I believe it would be very beneficial to you. Under his direction, with not too much money, I have been able to build my SR10 into a very accurate rifle. More so than my friend's Ares M110, which obviously has a longer barrel. I was making shots at about 275 feet with an almost 12 mph crosswind. Again, I recommend you find Vanevery's post and ask him some questions. I believe it's in community general chat.

well i wanted it to look like a dmr AND perform like one, i don't want a standard length rifle

Well if you want your gun to perform like a DMR, I don't think you want 590 mm barrel as you won't have enough air volume to propel the BB the distance you need. Your gun doesn't need to be a mile long to look like a DMR. People call my SR10 a DMR, and I don't even have the outer barrel on past the gas block. Just a suppressor.

well i wanted it to look like a dmr AND perform like one, i don't want a standard length rifle

Like pyro said, check out Vanavery's long range thread. that will help you out on the airsoft technical issues of getting your gun to shoot long range.
Also, you might want to rethink what a DMR looks like. It doesn't have to be a mile long to be a "DMR".
Mk12 SPR used by special forces - 18" barrel

Can you get away with using a 590mm Inner Barrel in your specific gun, yes.
You will need a Full / Type-O Cylinder and perfect Air Seal via a Gasket Sealant Mod.
I extensively tested a MadBull 590mm/6.03tbb in the early days of my DMR project.
Your shooting performance will be limited, even in the most perfect technical gun.

In terms of performance, you will shoot much farther and more accurate with a shorter barrel, even shorter than a 509mm standard m16 Inner Barrel. A 455mm is what will provide the best performance in regards to range and accuracy.

I'm also in the process of converting my RIS into a DMR. I use the 455mm 6.03 madbull and a g&g bucking. I just fixes my compression aand I was hitting a tree 200 feet away and the bb was still lifting. I use .3 bioval BBS. All that to say you don't need a 590mm barrel to get the longer shots. Have you read vaneverys long shot post? Tons of good info in there as he tests and documents like a boss.